Friction clutches of this type known, for example, from German Patent No. 23 14 006 B2 are utilized as dual clutches in utility machines, for example tractors, in which the combustion engine transmits the delivered torque via the dual clutch designed as a module to a dual-shaft transmission having two transmission input shafts, where two friction clutches operable independently of each other by means of a disengaging mechanism, transmit torque to a power take-off and/or to a speed-changing transmission.
The friction clutch has a traction mode, operating between the crankshaft of the combustion engine and the transmission input shaft of the speed-changing transmission, and has a module including an opposing pressure plate and a housing, which may be designed in a single piece or separately, having an axially displaceable pressure plate non-rotatably received on the latter, which is pre-stressed by means of a cup spring against the opposing pressure plate with friction linings of a clutch plate interposed. The pressure plate here is situated on the side facing away from the disengaging mechanism; relative to the opposing pressure plate, and is disengaged as well as tightened by means of knee levers subjected to axial force, which then displace pressure levers. At the same time, with the friction clutch in the engaged state, a pre-definable axial clearance of, for example, 2 mm is preset by means of adjusting screws situated between the pressure levers and the pressure plate. If wear occurs on the friction linings, this axial clearance is gradually reduced until the knee lever comes to rest on the disengaging mechanism. In this way, the effect of the cup spring relative to the pressure plate can be reduced so that the friction clutch slips and the friction linings may possibly be subjected to high thermal loads. To rectify this condition, a manual adjustment with the friction clutch in the installed state is possible only by means of the mechanical disengaging system between the pedal and friction clutch to adjust the axial clearance between knee lever and disengaging mechanism.